The present invention relates to a method for forming an air gap in an insulating film between adjacent interconnection conductors in a semiconductor device, in order to reduce a capacitance between the adjacent interconnection conductors.
In a semiconductor device, when a plurality of interconnection conductors are formed adjacent to each other at the same level in an insulating film, it is known to form an air gap between the adjacent interconnection conductors in order to reduce a capacitance between the adjacent interconnection conductors. This technology is disclosed by, for example, Japanese Patent Application Pre-examination Publication No.
JP-A-57-190331 (an English abstract of JP-A-57-190331 is available from the Japanese Patent Office and the content of the English abstract of JP-A-57-190331 is incorporated by reference in its entirety into this application), Japanese Patent Application Pre-examination Publication No. JP-A-09-055431 (an English abstract of JP-A-09-055431 is available from the Japanese Patent Office and the content of the English abstract of JP-A-09-055431 is incorporated by reference in its entirety into this application), Japanese Patent Application Pre-examination Publication No. JP-A-10-150103 (which corresponds to U.S. patent application Ser. No. 08/975,046 filed Nov. 20, 1997, the content of which is incorporated by reference in its entirety into this application, and an English abstract of JP-A-10-150103 is available from the Japanese Patent Office and the content of the English abstract of JP-A-10-150103 is incorporated by reference in its entirety into this application), and Japanese Patent Application Pre-examination Publication No. JP-A-10-229121 (an English abstract of JP-A-10-229121 is available from the Japanese Patent Office and the content of the English abstract of JP-A-10-229121 is incorporated by reference in its entirety into this application).
With an increased integration density of the semiconductor device, a spacing between adjacent interconnection conductors is decreasing more and more. When the spacing between adjacent interconnection conductors becomes small, however, the prior art process cannot satisfactorily or surely form between adjacent interconnection conductors an air gap which is effective in reducing the capacitance between the adjacent interconnection conductors.